A wide range of medical procedures involve the position and tracking of a catheter within a body. U.S. Patent Application 2007/0167722, which is incorporated herein by reference, describes methods and apparatus for locating the position, preferably in three dimensions, of a sensor by generating magnetic fields which are detected at the sensor. The magnetic fields are generated from a plurality of locations and, in one embodiment of the invention, enable both the orientation and location of a single coil sensor to be determined. The present invention thus finds application in many areas where the use of prior art sensors comprising two or more mutually perpendicular coils is inappropriate.
U.S. Patent Application 2010/0210939, which is incorporated herein by reference, describes a surgical navigation system for tracking an instrument relative to a patient. The system can track a portion of the patient, an instrument, and/or both relative to image data, a coordinate system, an atlas, a morphed atlas, or combinations thereof. The system can include a tracking device on the instrument to provide six degree of freedom information regarding the location of the instrument.
U.S. Pat. No. 7,277,834, which is incorporated herein by reference, describes a method for adapting electromagnetic (EM) field model parameters including the steps of minimizing the difference between a model for the measurements and one or more measurements. The minimization may be done by estimating model parameters, and at least position and/or orientation. The model may further include system model parameters, wherein the system may include one or more sensors and one or more radiators.
U.S. Pat. No. 6,335,617, which is incorporated herein by reference, describes a method for calibrating a magnetic field generator, including fixing one or more magnetic field sensors to a probe in known positions and orientations and selecting one or more known locations in the vicinity of the magnetic field generator. The magnetic field generator is driven so as to generate a magnetic field. The probe is moved in a predetermined, known orientation to each of the one or more locations, and signals are received from the one or more sensors at each of the one or more locations. The signals are processed to measure the amplitude and direction of the magnetic field, at the respective positions of the one or more sensors and to determine calibration factors relating to the amplitude and direction of the magnetic field in the vicinity of the magnetic field generator.
U.S. Pat. No. 5,307,072, which is incorporated herein by reference, describes a method and apparatus for determining the position and orientation of a remote object relative to a reference coordinate frame includes a source having a plurality of field-generating elements for generating electromagnetic fields, a drive for applying, to the generator element, signals that generate a plurality of electromagnetic fields that are distinguishable from one another, a remote sensor having a plurality of field-sensing elements for sensing the fields generated by the source, and a processor for processing the outputs of the sensing elements into remote object position and orientation relative to the source reference coordinate frame. The processor compensates the position and orientation values as a function of displacement of either the field-generating elements from a common center, or the field-sensing elements from a common center, or both. Techniques are disclosed for compensating for small-scale non-concentricity in order to overcome imperfections in the orthogonal coil sets wound on a common core, each set defining the source or the sensor. Techniques are also disclosed for compensating for large-scale non-concentricity to allow physical separation of the coil set defining the source or the sensor to dispersed locations that may be more desirable for a particular application.